The genetic regulatory mechanisms that govern tissue specific expression of the T cell receptor beta chain have been investigated utilizing an in vitro model of cell type specificity. A transient expression system has been used to assay the transcription of a genomic TCF beta chain gene (including 5 kb 5' of a rearranged V beta 1-J-C clone) in T cells, fibroblasts, and a variety of hematopoietic tumor cells. DNA sequencing of the V beta 1 leader and an additional 400 bp 5', in conjunction with S1 nuclease protection assays, has identified the start site of transcription. Also, a putative regulatory hexamer, CTTTCT, that is conserved in several human and murine V beta genes has been identified approximately 250 bp 5' to the mRNA cap site. Transfection efficiencies were normalized by determining the mRNA levels of a truncated histone gene contained within the plasmid vector as a tissue nonspecific control. Unlike immunoglobulin genes, expression of a rearranged C beta 1 gene was found in nonlymphoid cells. However, it was observed that T cells show a minimum of a 3 fold preferential expression of the beta chain as compared to fibroblasts and monocytic cells. Furthermore, a 1.5 kb deletion in the 5' region of the J beta 1 - C beta 1 intron does not preclude beta chain expression in T cells or fibroblasts. Tissue specific regulation of T cell receptor beta chain expression does not appear to require gene sequences within this region of the intron, but may be influenced by a conserved region of the gene 5' to the promotor.